Optical fiber, optical sensor including optical fiber, method of manufacturing optical fiber, and deposition apparatus therefor

ABSTRACT

Disclosed is an optical fiber including a plasmonic optical filter with a closed curved shape provided at, at least portion thereof. A method of manufacturing the plasmonic optical filter includes a step of exposing a core, a step of forming a thin metal film on the core through physical vapor deposition while rotating the core in a circumferential direction after changing a rotation axis of the core, and a step of patterning nanopatterns on the cylinder-shaped thin metal film using focused ion beam technique assisted with endpoint detection method. Due to such constitutions, an active area to generate an optical signal for optical sensor can be increased.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional Application of U.S. application Ser.No. 15/280,183, filed Sep. 29, 2016, which claims priority to and thebenefit of Korean Patent Application No. 10-2015-0170051, filed on Dec.1, 2015, the disclosure of which is incorporated herein by reference inits entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an optical fiber, an optical sensorincluding optical fiber, a method of manufacturing the optical fiber,and a deposition apparatus for them, and more particularly to metallicstructures on the side of an optical fiber for increasing an opticalsignal generation area, an optical sensor including optical fiber, amethod of manufacturing the optical fiber, and a deposition apparatusfor them.

2. Description of the Related Art

Recently, fiber-optic refractive index sensors utilizing surface plasmonresonance have been developed. Optical fibers have a superiorelectromagnetic interference shielding characteristic, fast responsetime, and ability to achieve long-distance transmission, but the sizesthereof are small. Accordingly, such optical fibers are used asplatforms of biological/chemical sensors in various fields, e.g.,microenvironments, such as blood vessels, carbon dioxide geologicstorage facilities, and the like.

Meanwhile, existing refractive index sensors using the optical fibershave optical filter, which includes plasmonic structures, at end facesof the fibers. By the way, since an area of the optical filter islimited to a small area of the end face, a small amount of opticalsignals are disadvantageously generated. Accordingly, research into anoptical fiber for increasing the amount of optical signals and a sensorusing the optical fiber is underway.

RELATED ART DOCUMENT Patent Document

(Patent Document 1) Korean Patent No. 10-1136258 (registration date:Apr. 5, 2012)

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the aboveproblems, and it is an object of the present invention to provide anoptical fiber including plasmonic optical filter for increasing anoptical signal generation area, an optical sensor having the same, amethod of manufacturing the optical fiber, and a deposition apparatusfor them.

In accordance with the present invention, the above and other objectscan be accomplished by the provision of an optical fiber, wherein aplasmonic optical filter having a closed curved shape is provided to atleast a portion of the optical fiber.

According to an aspect, the plasmonic optical filter may be formed bypattering a thin metal film formed into a cylindrical shape at a portionof a circumferential surface of an exposed core with nanopatterns.

According to an aspect, the thin metal film may be made of at least oneof gold, silver, aluminum, and chrome.

According to an aspect, the nanopatterns may include a plurality ofholes perforating the thin metal film.

According to an aspect, the nanopatterns may be periodically arrangedside by side.

In accordance with another aspect of the present invention, there isprovided an optical sensor including: a core; a cladding surrounding aportion of the core and made of a material having a lower refractiveindex than a material of the core; and an optical filter formed into acylindrical shape at another portion of the core and including a thinmetal film patterned with nanopatterns.

In accordance with another aspect of the present invention, there isprovided an optical sensor including: a light source for generatinglight; a probe for sensing the light guided to a target and transmitted,at least a portion of the probe including an optical fiber that includesa plasmonic optical filter having a closed curved shape; and a detectorfor detecting the target by detecting light transmitted from the probe.

According to an aspect, the optical sensor includes: input and sensingports provided between the light source and probe and guiding input andsensing of the light; and a detection port provided between the probeand the detector and guiding detection of the light.

In accordance with another aspect of the present invention, there isprovided an optical sensor, including: a light source for generatinglight; a probe for sensing the light guided to a target and beingreflected, at least a portion of the probe including an optical fiberthat includes a plasmonic optical filter having a closed curved shape; adetector for detecting the target by detecting the light reflected fromthe probe; and a circulator for circulating the light in an order of thelight source, the probe, and the detector, the circulator being providedamong the light source, the probe, and the detector.

According to an aspect, the optical sensor may include: an input portfor guiding input of light, the input port being provided between thelight source and the circulator; a sensing port for guiding sensing oflight, the sensing port being provided between the probe and thecirculator; and a detection port for guiding detection of light, thedetection port being provided between the detector and the circulator.

In accordance with another aspect of the present invention, there isprovided a method of manufacturing the optical fiber, the methodincluding: exposing a core; forming a thin metal film on the corethrough physical vapor deposition, for example using an evaporator,while rotating the core in a circumferential direction; and patterningat least one nanopattern on the thin metal film to forming form aplasmonic optical filter.

According to an aspect, the exposing may include removing a cladding anda jacket surrounding an outer circumference of the core.

According to an aspect, the forming may include: inserting the core intoa guider for changing a rotation axis of the core, inside a vacuumchamber; rotating the core in a circumferential direction in a state inwhich the guider is inserted into the guider; andphysical-vapor-depositing the core, a metal source of which is exposed,in a cylindrical shape.

According to an aspect, the guider may be made of Teflon, includes apenetrated open window for exposing the core formed at a location facingthe metal source, is curved to change a rotation axis of the core, andmay have a hollow tube shape, wherein a diameter of the guider isgreater than a diameter of the core.

According to an aspect, the open window may be coupled with a maskincluding at least one penetrated open hole through which the metalsource passes.

According to an aspect, in the patterning, at least one nanopattern mayinclude a plurality of perforated holes patterned side by side bymachining the thin metal film by a focused ion beam system whiledetecting a real-time machined surface for machining endpoint detection.

In accordance with yet another aspect of the present invention, there isprovided a deposition apparatus for manufacturing a plasmonic opticalfilter, including: a vacuum chamber; a guider which includes an openwindow formed at a portion of the guider and is provided inside thechamber, into which the optical fiber, a core of which is exposed byremoving a cladding from the optical fiber, is inserted, and which iscurved to change a rotation direction of the optical fiber; a drivingunit for rotating the optical fiber, the driving unit being insertedinto the guider; and a deposition unit for depositing a metal source onthe core exposed through the open window.

According to an aspect, the guider may be made of Teflon and may have ahollow tube shape having a larger diameter than the optical fiber.

According to an aspect, the guider may include a curve unit curved intoan L-shape such that the optical fiber is disposed at a location facingwith the deposition unit, and has a hollow tube shape.

According to an aspect, the open window may be coupled with a mask thatincludes at least one penetrated open hole through which the metalsource passes.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a perspective view schematically illustrating an optical fiberaccording to a preferred embodiment of the present disclosure;

FIG. 2 is a flowchart schematically illustrating a method ofmanufacturing the optical fiber illustrated in FIG. 1;

FIG. 3 is a perspective view schematically illustrating a core-exposedoptical fiber to describe a step of exposing a core illustrated in FIG.2;

FIG. 4 schematically illustrates a deposition apparatus formanufacturing a plasmonic optical filter to describe a step of forming athin metal film illustrated in FIG. 2;

FIG. 5 schematically illustrates examples of a mask that may beinstalled at an open window of a guider illustrated in FIG. 4;

FIGS. 6A and 6B illustrate a spacing distance between a core and a metalsource from different directions;

FIG. 7 is a schematic view to describe Langmuir-Knudsen equation;

FIG. 8 is a sectional view schematically illustrating a state in which acylindrical thin metal film is uniformly formed in a circumferentialdirection of a core;

FIGS. 9A and 9B schematically illustrate images of cylindrical thinmetal films deposited on cores;

FIG. 10 schematically illustrates various deposition shapes of a thinmetal film due to control of the rotation speed of a core;

FIG. 11 is a graph schematically illustrating gray levels of secondaryelectron images that are monitored while focused ion beam machining inorder to detect machining endpoint;

FIG. 12 schematically illustrates focused ion beam machining statuses inthe (A) and (B) sections of the gray level graph illustrated in FIG. 11;

FIGS. 13A and 13B schematically compare machining error occurring whennano-patterning is performed on a thin metal film deposited at a side ofa core with a precisely machined state using machining endpointdetection;

FIGS. 14A and 14B schematically illustrate an embodiment of a plasmonicoptical filter including a plurality of nanopatterns with various shapesand a light transmission spectrum obtained due to the nanopatterns;

FIGS. 15A and 15B schematically compare light transmission states of anoptical fiber with a thin metal film only and an optical fiber accordingto the present disclosure;

FIG. 16A illustrates an image of a light transmission state using anoptical fiber with a thin metal film only;

FIG. 16B illustrates an image of a light transmission state using anoptical fiber according to the present disclosure;

FIG. 17 schematically illustrates a transmission-type sensing systemincluding an optical fiber according to the present disclosure; and

FIG. 18 schematically illustrates a reflective-type sensing systemincluding an optical fiber according to the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, preferred embodiments of the present disclosure aredescribed with reference to the accompanying drawings.

Referring to FIG. 1, the optical fiber according to a preferredembodiment of the present disclosure 1 includes a cylindrical plasmonicoptical filter 40 in at least a portion thereof. The optical fiber 1 mayinclude a core 10, a cladding 20, a jacket 30, and a plasmonic opticalfilter 40.

The core 10 is disposed at the center of the optical fiber 1 may be madeof a material having a relatively high refractive index, such ascylindrical silica.

The cladding 20 may surround a portion of the core 10, and may be madeinto a hollowed cylindrical shape such that the core 10 passes throughthe interior of the cladding 20. The cladding 20 may be made of amaterial, such as silica, having a smaller refractive index than thematerial of the core 10 such that light proceeding in the interior ofthe core 10 is totally reflected.

Although the optical fiber 1 according to the embodiment of the presentdisclosure includes both the core 10 and the cladding 20, the opticalfiber 1 may include any one of the core 10 and the cladding 20, thushaving a single refractive index. More particularly, when the opticalfiber 1 has a single refractive index by including any one of the core10 and the cladding 20, the optical fiber 1 may be formed into astructure in which a thin metal film is laminated on a fiber side of thecore 10 or the cladding 20 having a single refractive index.

The jacket 30 may surround the cladding 20 and may protect the core 10and the cladding 20 from external impact. The jacket 30 may be made of asynthetic resin coating material.

The optical filter 40 may be provided at a portion of the core 10,except for a portion surrounded by the cladding 20. The optical filter40 may include a thin metal film 41, which is deposited on the core 10,and nanopatterns 42, which are formed by patterning the thin metal film41. The nanopatterns 42 formed at the thin metal film 41 of the opticalfilter 40 may be nanoholes formed by perforating the thin metal film 41at nanometer scale.

The thin metal film 41 may be made of at least one of gold, silver,aluminum, and chrome. The optical filter 40 may exhibit surface plasmonresonance effect, by which the optical filter 40 can filterspecific-wavelength light out, due to the nanopatterns 42 formed at thethin metal film 41. The wavelengths of light may be varied dependingupon the refractive indexes of medium near the optical filter 40.Accordingly, using such a phenomenon, change of medium near the opticalfilter 40 may be detected by monitoring wavelengths of the transmittedlight.

In addition, surface plasmon resonance effect depends upon thearrangements and sizes of the nanopatterns 42 formed in the thin metalfilm 41. Further, the wavelengths of light filtered out at the opticalfilter 40 may be different depending upon the arrangements and sizes ofthe nanopatterns 42.

A method of manufacturing the optical fiber 1 including the opticalfilter 40 includes a step of exposing the core 100, a step of forming athin metal film 200, and the nano-patterning step 300, as illustrated inFIG. 2.

Hereinafter, the method of manufacturing the optical fiber 1 issequentially described and the configuration of the optical fiber 1 isalso described.

In the step of exposing the core 100, the cladding 20 and the jacket 30among the core 10, the cladding 20 and the jacket 30 constituting theoptical fiber 1 are removed such that the core 10 is exposed, asillustrated in FIG. 3. Here, the jacket 30 may be physically, easilyremoved, whereas the cladding 20 may be removed by a special machiningmethod, such as plasma etching or laser etching, or a chemical method,such as a wet etching method. In an embodiment of the present invention,the cladding 20 is removed using wet etching. However, when the opticalfiber 1 includes any one of the core 10 and the cladding and thus has asingle refractive index as described above, wet etching may beunnecessary.

The step of removing the cladding 20 by the wet etching method isdescribed in detail. First, an optical fiber 1 including a step-indexsingle-mode optical fiber or multimode optical fiber is prepared.Subsequently, a resultant optical fiber 1 or a plurality of resultantoptical fibers 1 are immersed in an etching solution to be etched. Here,the ingredients of the core 10 and the cladding 20 of the optical fiber1 are pure silica and F-doped silica, respectively. The etching solutionincludes hydrogen fluoride (HF) having high reactivity and thus allowingrapid etching of silica. An etched optical fiber 1 is washed withdeionized water, although this is not illustrated in detail.

In the step of forming a thin metal film 200, a closed cylindrical thinmetal film 41 is formed on a circumferential surface of the core 10exposed by shifting a rotation axis of the optical fiber 1 and rotatingthe shifted rotation axis. To accomplish this process, the physicalvapor deposition apparatus, which is an evaporator in the presentinvention, 50 for manufacturing the optical filter 40 as illustrated inFIG. 4 is used in the step of forming a thin metal film 200.

The deposition apparatus 50 includes a vacuum chamber 51, a guider 52,the driving unit 53, and a deposition unit 54.

Since the interior of the chamber 51 is under vacuum, an environment inwhich the cylindrical thin metal film 41 is deposited by physical vapordeposition in a circumferential direction of the core 10 is provided.

The guider 52 is provided in the interior of the chamber 51. The guider52 is manufactured into a hollow shape such that the optical fiber 1,from which the cladding 20 is removed to expose the core 10, can beinserted. In addition, the guider 52 includes an open window 52 a, whichis formed at a portion of the guider 52, and the curve unit 52 b, whichis curved to change a rotation direction of the optical fiber 1. Thecurve unit 52 b of the guider 52 is provided to adjust a rotation axisof the optical fiber 1 having a flexible property. In an embodiment ofthe present invention, the rotation axis of the optical fiber 1 ischanged to an angle of 90. That is, the guider 52 is curved in adirection facing the deposition unit 54 described below, thus guidingthe optical fiber 1 to face the deposition unit 54.

For reference, the curve unit 52 b is provided at a minimum to inhibitfriction between the optical fiber 1 and the guider 52 which may occurduring the rotation of the optical fiber 1. In an embodiment, the guider52 of the present disclosure connects a rotation shaft of the drivingunit 53, which is described below, to a side of the optical fiber 1 andincludes a single curve unit 52 b curved into an L-shape.

In addition, the guider 52 is made of Teflon having superioranti-chemical properties and heat resistance. Further, since the guider52 is manufactured into a hollow shape while having a diameter largerthan that of the optical fiber 1, friction between the guider 52 and theoptical fiber 1 does not occur although the optical fiber 1 operates inthe interior of the guider 52. For reference, when friction occursbetween the guider 52 and the optical fiber 1, shearing modulusincreases and, at the same time, torsional elastic energy increases,whereby energy transfer efficiency of the optical fiber 1 decreases.

The driving unit 53, which is included in commercial physical vapordeposition apparatuses (hereinafter referred to as a commercialapparatus, not shown), is used to improve the uniformity of a thin filmby rotating a substrate, such as silicon substrate, in a circumferentialdirection. In the present disclosure, the aforementioned guider 52 isadditionally installed at a commercial apparatus to transfer rotationalforce generated by the driving unit 53, which is included in thecommercial apparatus, to the optical fiber 1.

When the optical fiber 1 is rotated by the driving unit 53 which isconnected to a side of the optical fiber 1 inserted into the guider 52,the rotation is transferred to another end of the optical fiber 1 by theguider 52 which is curved at an angle of 90° and has the core 10.Accordingly, the other area of the optical fiber 1 inserted in theguider 52 rotates in a circumferential direction. For reference,although the optical fiber 1 in the interior of the guider 52 is rotatedby the driving unit 53, the guider 52 is supported by the supporter 52a, thus being fixed in position.

With regard to the deposition unit 54, the core 10 exposed through theopen window 52 a of the guider 52 is deposited with a metal source 54 a.The deposition unit 54 is disposed such that the optical fiber 1inserted into the guider 52 is perpendicular to an evaporation directionof the metal source 54 a, and thus, the optical fiber 1 is depositedwith the thin metal film 41. Here, the thin metal film 41 depositedthrough the deposition unit 54 is formed of the metal source 54 aincluding at least one of gold, silver, aluminum, and chrome.

Referring to FIG. 5, examples of a mask, M1, M2, and M3, which areinstalled at the open window 52 a of the guider 52 and may be coupledwith the guider 52, are schematically illustrated. As illustrated inFIG. 5, each of the masks M1, M2, and M3 that may be installed at theopen window 52 a includes at least one open hole of H1, H2, and H3having different shapes. That is, the masks M1, M2, and M3 illustratedin FIG. 5(a), (b), and (c) have different widths and at least one ofperforated open holes, H1, H2, and H3. The shapes, sizes, and numbers ofthe open holes, H1, H2, and H3, are not limited to the embodimentsillustrated in (a), (b) and (c) of FIG. 5. Due to the masks M1, M2, andM3 with various open hole shapes, H1, H2, and H3, installed at the openwindow 52 a, the thin metal film 41 may be laminated on the core 10 invarious shapes.

Meanwhile, as illustrated in FIG. 6A, the exposed core 10 of the opticalfiber 1 is disposed in a perpendicular direction to an evaporationdirection of the metal source 54 a, and thus, the cylindrical thin metalfilm 41 is deposited when the core 10 is rotated in a circumferentialdirection. Meanwhile, as illustrated in FIG. 6B, rectilinear motion ofthe optical fiber 1 may occur by runout due to a difference in diameterbetween the optical fiber 1 and the guider 52. As illustrated in FIGS.6A and 6B, the rotational and rectilinear motions of the optical fiber 1allow distances r1 and r2 between the core 10 and the metal source 54 ato be maintained while the thin metal film 41 is vapor-deposited alongthe circumference of the core 10.

For reference, to uniformly laminate the thin metal film 41 on the core10 using vacuum vapor deposition, a deposition speed of the metal source54 a should be kept constant. Here, the deposition speed of the metalsource 54 a is determined by a deposition location determined by theangle (θ, Φ) of the center of a side of each of the metal source 54 aand the base substrate, the core 10, and distances r1 and r2 accordingto the Langmuir-Knudsen equation disclosed in Equation 1 below:

$\begin{matrix}{R_{m} = {{C\left( \frac{M}{T} \right)}^{0.5}\cos\;\theta\;\cos\;\phi\;\frac{1}{r^{2}}\left( {P_{e} - P} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In the equation, C represents a constant value of 1.85×10⁻², Mrepresents molecular weight, r(cm) represents a distance between themetal source 54 a and the core 10, T(k) represents the temperature ofthe metal source 54 a, P_(e) (torr) represents a steam pressure as afunction of T, and P represents the pressure of the chamber 51 (see FIG.7). For reference, P becomes 0 under high vacuum.

The thin metal film 41 deposited on the exposed core 10 of the opticalfiber 1 by means of the deposition apparatus 50 is uniformly formed as aclosed curved surface, i.e., into a cylindrical shape, along thecircumference of the core 10, as illustrated in FIG. 8. FIGS. 9A and 9Billustrate images of aluminum thin films uniformly laminated to athickness of 100 nm on the core 10 of the optical fiber 1.

Meanwhile, as illustrated in FIG. 10, the cylindrical thin metal film 41may be formed into various shapes along the circumferential direction ofthe core 10 of the optical fiber 1 by changing the rotation speed of theoptical fiber 1. For reference, since the characteristics of transmittedlight depend upon the shapes of the thin metal film 41, the thin metalfilm 41 may be utilized as a platform for various plasmonic opticalfilters 40.

When the thin metal film 41 is formed, the nanopatterns 42 are formed atthe cylindrical thin metal film 41 (step 300). In the patterning step(step 300), the core 10 is machined using a focused ion beam (I)assisted with a machining endpoint detection method investigating areal-time machined surface 41, thereby patterning the nanopatterns 42including a plurality of holes. However, the method of forming holes inthe thin metal film 41 is not limited to the machining endpointdetection method and any method of forming nanoscale holes at the thinmetal film 41 may be used.

In particular, machined depths may be different upon machining withfocused ion beam (I) since a surface of the cylindrical thin metal film41 formed on the core 10 is curved, and thus, the machining endpointdetection method is used. Upon machining with the focused ion beam (I)assisted with the machining endpoint detection method, a time point atwhich a material of a machined surface is changed as illustrated in FIG.11 is detected as a machining endpoint using SE images of a machinedsurface of the thin metal film 41 measured in real-time.

A time point at which the machined surface, i.e., the surface materialof the thin metal film 41, is changed, may be detected by monitoring thegray level of an SE image as illustrated in FIG. 11. Here, asillustrated in FIG. 11, a time point at which a graph is kept constantafter a temporal change of the graph corresponds to a machining endpoint(t_(END)) at which a material of the thin metal film 41 is completelychanged.

For reference, FIG. 12 illustrates focused ion beam machining states insections (A) and (B) of the gray level graph illustrated in FIG. 11. Inaddition, FIGS. 13A and 13B illustrate states in which a machining erroroccurs upon nano-patterning of the thin metal film 41 deposited at aside of the core, and a precisely machined state using the machiningendpoint detection method. As such, the precision of nano-patterning ofthe cylindrical thin metal film 41, i.e., the thin metal film 41 formedin a cylindrical shape, formed on the core 10 is improved throughmachining endpoint detection.

In an embodiment of the present invention, the nanopatterns 42, whichare machined using focused ion beam (I) equipment using the machiningendpoint detection method, is arranged into a bowie-shaped holes arrayhaving a size of about 0.7 μm*1.16 μm, although not described in detail.

Referring to FIGS. 14A and 14B, another embodiment of nanopatterns 42′is illustrated. The nanopatterns 42′ illustrated in FIG. 14A include thefirst to third patterns 42 a′, 42 b′, and 42 c′ which are provided atthe thin metal film 41, have different pattern shapes, are spaced fromeach other, and are arranged side by side. That is, the nanopatterns 42′include a plurality of nanopatterns, i.e., the first to third patterns,42 a′, 42 b′, and 42 c′, including a plurality of holes formed intodifferent patterns. With regard to optical signals generated by theoptical fiber 1 that includes the nanopatterns 42′ including the firstto third patterns, 42 a′, 42 b′, and 42 c′, as illustrated in FIG. 14B,the first to third patterns 42 a′, 42 b′, and 42 c′ exhibit differentplasmon resonance frequencies (λ₁, λ₂, and λ₃), respectively.

Here, the sensitivities of resonance frequencies (λ₁, λ₂, and λ₃) of thenanopatterns 42′ including the first to third patterns 42 a′, 42 b′, and42 c′ differ depending upon refractive index changes (Δn) in ambientmedia. For example, a change in the refractive index gradually increasesin an order of the first pattern 42 a′, the second pattern 42 b′, andthe third pattern 43 c′. Accordingly, the nanopatterns 42′ including thefirst to third patterns 42 a′, 42 b′, and 42 c′ may provide improvedmeasurement precision compared to the single-shaped nanopatterns 42illustrated in FIG. 1 and, at the same time, is advantageous inmeasuring various materials.

Light transmission quality of the optical fiber 1 including theplasmonic optical filter 40 manufactured as described above is comparedto a conventional optical fiber as illustrated in FIGS. 15A, 15B, 16Aand 16B.

FIG. 15A illustrates the spectrum of light transmitted through aconventional optical fiber not including the optical filter 40. FIG. 15Billustrates the spectrum of light transmitted through the optical fiber1 including the optical filter 40 according to the present disclosure.As illustrated in FIGS. 15A and 15B, the optical fiber 1 including theplasmonic optical filter 40 exhibits a superior spectrum result of thetransmitted light.

In addition, FIG. 16A illustrates a state of light transmitted throughthe conventional optical fiber not including the optical filter 40, andFIG. 16B illustrates a state of light transmitted through the opticalfiber 1 including the plasmonic optical filter 40 according to thepresent disclosure. In FIG. 16A, when white light is transmitted, yellowlight is transmitted. On the other hand, in FIG. 16B, by using theplasmonic optical filter 40, white light is filtered into green light.

For reference, a transmission-type optical sensor that includes theoptical fiber 1 of the present disclosure including the optical filter40 is illustrated in FIG. 17. As illustrated in FIG. 17, light inputfrom the light source L is sensed by a probe including the optical fiber1 via first and second ports P1 and P2 and then passes through a thirdport P3, followed by being detected by a detector D. Here, the firstport P1 is an input port for guiding input of light, the second port P2is a sensing port for guiding sensing of light, and the third port P3 isa detection port for guiding detection of light.

In addition, a reflective-type optical sensor that includes the opticalfiber 1 including the optical filter 40 is illustrated in FIG. 18. Asillustrated in FIG. 18, light, which circulates from the light source Lto an input port, a first port P1, via a circulator C, passes through asensing port, a second port P2, and then is sensed by a probe includingthe optical fiber 1. The sensed light is reflected by a circulator C andcirculated again. Accordingly, the light is detected in the detector Dvia a detection port, the third port P3.

The optical fiber 1 including the plasmonic optical filter 40 hasincreased filtering and sensing areas and thus may be applied as asuperior optical filter and optical sensor. In addition, the opticalfiber 1 may be variously applied even in microenvironments, such asblood vessels, or severe environments requiring long-distancetransmission ability, such as geologic storage facilities.

According to the present invention having the aforementionedconfiguration, first, a plasmonic optical filter is provided at theexposed core of the optical fiber and thus an optical signal generationarea increases, which contributes to efficiency increase.

Second, by applying thin-film coating technology limitedly used to flatsubjects to be machined while adjusting a rotation axis of an opticalfiber, freeform and curved micro devices can be manufactured.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

DESCRIPTION OF SYMBOLS

-   -   1: OPTICAL FIBER 10: CORE    -   20: CLADDING 30: JACKET    -   40: OPTICAL FILTER 50: DEPOSITION APPARATUS    -   51: CHAMBER 52: GUIDER    -   53: DRIVING UNIT 54: DEPOSITION UNIT

What is claimed is:
 1. An optical sensor, comprising: a light source forgenerating light; a probe for sensing the light guided to a target andtransmitted, at least a portion of the probe comprising an optical fiberthat comprises a plasmonic optical filter having a closed curved shape;and a detector for detecting the target by detecting light transmittedfrom the probe, wherein the plasmonic optical filter is formed bypatterning a thin metal film formed into a cylindrical shape at aportion of a circumferential surface of an exposed core withnanopatterns, wherein the nanopatterns comprise a plurality of holesperforating the thin metal film, and wherein the nanopatterns areprovided in a plurality of different patterns and are arranged side byside spaced apart from each other.
 2. The optical sensor according toclaim 1, comprising: input and sensing ports provided between the lightsource and probe and guiding input and sensing of the light; and adetection port provided between the probe and the detector and guidingdetection of the light.
 3. An optical sensor, comprising: a light sourcefor generating light; a probe for sensing the light guided to a targetand being reflected, at least a portion of the probe comprising anoptical fiber that comprises a plasmonic optical filter having a closedcurved shape; a detector for detecting the target by detecting the lightreflected from the probe; and a circulator for circulating the light inan order of the light source, the probe, and the detector, thecirculator being provided among the light source, the probe, and thedetector, wherein the plasmonic optical filter is formed by patterning athin metal film formed into a cylindrical shape at a portion of acircumferential surface of an exposed core with nanopatterns, whereinthe nanopatterns comprise a plurality of holes perforating the thinmetal film, and wherein the nanopatterns are provided in a plurality ofdifferent patterns and are arranged side by side spaced apart from eachother.
 4. The optical sensor according to claim 3, comprising: an inputport for guiding input of light, the input port being provided betweenthe light source and the circulator; a sensing port for guiding sensingof light, the sensing port being provided between the probe and thecirculator; and a detection port for guiding detection of light, thedetection port being provided between the detector and the circulator.